问题 问答题 论述题

叙述沉积岩中同生变形构造的类型及特征。

答案

参考答案:

沉积过程中,或在沉积后不久且在沉积物固结前,由沉积物塑性变形而形成的构造,统称为同生变形构造。多产于快速堆积、沉积坡度较大的环境,如三角洲前缘、斜坡带等。

负荷构造:是指覆盖泥质岩之上的砂层底面上的瘤状突起。特征:负载构造形状很不规则,一般不对称,排列杂乱,大小不一,从几毫米到几分米。成因:由于下伏的含水塑性软泥承受了不均匀的负载,使上覆砂质物陷入下伏泥质物中而产生。

火焰状构造:当下伏软泥中的纹层发生畸变时,常被向上挤入夹于下垂的负载构造之间,呈薄的舌状体,称之为火焰构造

球状与枕状构造:这种构造是指砂岩层断开并陷入泥岩中形成的许多紧密或稀疏的椭球状或枕状块体。特征:大小可从直径几厘米至一米,甚至几米。一般不具内部构造,如果砂岩具有纹层,则多已变形,常随砂球或砂枕外形向下弯曲而呈槽状。成因:砂层断裂陷入下伏泥质岩中形成。不限于任何特殊的环境

旋转层理:在一个岩层内所发生的纹层盘回和扭曲现象。特征:常限于一个层内连续分布,并显示出小型开阔向斜和紧密背斜的复杂现象。这些褶曲常常是顺水流方向倒转,且褶曲轴大致平行,不伴随断裂和角砾化现象。成因:液化层的层间流动引起原生层理的弯曲。分布:见于软弱层(2-25cm)粗粉砂层或细粉砂层及硅质、碳酸盐质层中。浊流沉积中较为常见。

碟状构造:快速堆积的松散沉积物中,孔隙水向上泄出,引起颗粒的位移和重新排列,形成泄水构造,如碟状构造、柱状构造。主要见于浊流沉积、三角洲前缘沉积及河流边滩沉积。

滑塌构造:指斜坡上未固结的软沉积物在重力作用下发生滑动而形成的变形构造。各种类型的不规则的扭曲层理也属于滑塌构造。特征:沉积层内发生变形、揉皱,常伴随小型断裂,甚至使岩石破碎、岩性混杂,呈角砾状外貌等。成因:滑塌构造一般伴随快速沉积而产生。它是水下滑坡的良好标志。多分布在潮间滩地的水道内与河道中的点砂坝,三角洲前缘以及海底峡谷前缘等。

鸡笼铁丝网状构造:在潮上带的蒸发岩中,结核状的硬石膏与纹层状白云岩互层,经过压实作用,硬石膏结核密集,而白云岩纹层弯曲形成鸡笼铁丝网状构造。它是蒸发环境的指相构造。

帐篷构造:主要出现在潮坪白云岩中,当白云岩与石膏或硬石膏成交互纹层时,由于石膏的脱水或硬石膏的水化,引起岩石的体积收缩或膨胀;或者由于颗粒沉积物中胶结物晶体的生长使岩石发生破裂;或者由于温度极大的变化引起岩石的破裂等,由以上作用所形成的倒伏的倒“V”字形构造(纵剖面)。在一个层内倒“V”字形构造的间距有几厘米至几十厘米,高几毫米至几厘米,横断面似干裂多边形。

选择题
阅读理解

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

     A man was driving at 70 miles in a 40-mile-zone, when a police car came behind him with the light on.

1.____

     As the policeman came to him, he said, "Hi, officer, I guess you caught me a little bit over the limit. I was

in a rush to get home, to be with my wife and kids, you know my younger son wasn't feeling too well when

I left home this morning.

     The policeman said, "Well, I guess so," and started writing something in his notebook. 2.____ Afew

moments later, the policeman came to his window and handed him a paper, and returned to his car without

saying a single word. The man started to wonder, how much this ticket was going to be as he began to look

at the paper. 3.____

     "I had a daughter who was killed by a speeding car at the age of six, by a speeding driver like you. He got

a fine, a few months in prison, and was free, free to hug two other daughters. 4.____ I have tried to forgive

that man a thousand times, and I thought I had. Maybe I really did forgive him, but I have to do it again, even

right now. 5.____

     The man was very surprised and could not move for the next few minutes. When finally he did, he drove

slowly, even a few miles under the speed limit, praying for forgiveness.

A. So pray for you, and be careful when you drive again, your daughter is all you have left.

B. I only had one, and now I have to wait I go to heaven before I can hug her again.

C. Right away the man started thinking of excuse to give.

D. He was surprised it was not a ticket as he began to look at.

E. So pray for me, and be careful when you drive again, my son is all I have left.

F. As minutes went by, he hadn't asked for his driver's license.

G. He was surprised it was not a ticket as he began to read.